FIG. 1 is a view in perspective of a module 1 for rapid interconnection of telephone lines and for protection against lightning or other overvoltages, which is at present marketed by Applicants, while FIG. 2 is an exploded view in perspective of its intermediate half-bushing 2 forming a protection device against lightning or other overvoltages.
It is briefly recalled here that this module 1 is mounted on a preferably standardized metal rail 3 which constitutes an electrical earth connection bar, and that it is constituted by three superposed half-bushings or rings:
a lower half-bushing 4 which receives the first pair of telephone lines, PA1 an intermediate half-bushing, called "protection ring" in which is plugged a protection module 5 containing a three-pole lightning arrester or "overvoltage arrester" 6, and PA1 an upper half-bushing 7 which receives the second pair of telephone wires. PA1 in that it comprises, in a receptacle for receiving the overvoltage arrester, three elastic metal contacts, viz. a median earth connection contact whose transverse section presents the form of a two-tined fork which is provided to receive, between these two tines, the median annular earth electrode of the overvoltage arrester, and two lateral line connection contacts which are respectively positioned on either side of this earth contact and symmetrically with respect to the median transverse plane thereof, each of these two contacts being provided to elastically abut respectively against the two line electrodes of the overvoltage arrester, PA1 in that the internal dimensions of said receptacle are slightly greater than the average dimensions of an overvoltage arrester available on the market, with the result that, taking into account the clearance allowed by the elasticity of these three elastic contacts, this receptacle is adapted to receive commercially available overvoltage arresters whose external dimensions may be slightly different from one another, PA1 in that said median elastic earth connection contact is in the form of a cradle which comprises, in the longitudinal direction parallel to the axis of the overvoltage arrester and on either side of each of the two elastic earth connection lugs which form the two tines of said fork, respectively two additional elastic metal lugs which are shaped in order respectively to abut on each of the two line electrodes of the overvoltage arrester, an insulating shim made of thermofusible material being, in addition, provided to be inserted between each of these four additional elastic lugs and the body of the overvoltage arrester in order, by application of a well known general means, normally to form an electrically insulating gap, generally an air gap, between each additional lug and its conjugate line electrode of the overvoltage arrester, this insulating gap being eliminated when, the overvoltage arrester having just functioned, this insulating shim then melts under the effect of the heat, and PA1 in that this thermofusible shim comprises four adjusting tabs which are respectively adapted to fit, when said shim is positioned, between each of said additional elastic metal lugs.
A median screw 8 traverses the assembly of the module 1 and serves both as earth connection and as clamping device ensuring cohesion of the three half-bushings and ensuring self-stripping connections of the four line wires.
The protection ring 2 is composed (FIG. 2) of a body 9 of plastics material which firmly houses three "tuning-fork" contacts, viz. a central double tuning-fork contact 10 which receives the body of the screw 8 and is therefore the earth contact, and two lateral tuning-fork contacts 11 and 12 which are connected to the two line terminals of the module.
The plug-in protection module 5 is composed of a body 13 of plastics material which forms a receptacle for a lightning arrester or overvoltage arrester 6.
This overvoltage arrester 6 is a three-pole lightning arrester found on the market, on the three electrodes of which are soldered three rigid contact lugs 70, 71, 72 which are provided to traverse the bottom of the receptacle 13 so as to plug respectively in the contacts 10, 11, 12 when the module 5 is plugged on the protection ring 2.
After assembly of the protection module 5, the overvoltage arrester 6 is embedded in a polyurethane resin 74 (FIG. 1).
This known device presents drawbacks:
The fact that the overvoltage arrester is embedded in a very rigid polyurethane resin necessitates coating this overvoltage arrester with a layer of a supple product, such as a product based on silicone, in order to allow the fusible device for thermal limitation, which is conventionally interposed between the earth of the lightning arrester and at least one line electrode, to perform its role fully despite the presence of the polyurethane which is rigid. This arrangement increases the cost of this protection module.
An overvoltage arrester, on whose electrodes contact lugs are soldered is not a product available on the market. Consequently, it is not possible for the user to replace the plug-in protection module of the lightning arrester after said lightning or overvoltage arrester has functioned: the whole of the module must be changed, which is relatively expensive.
In addition, this known device is provided to receive an overvoltage arrester of well-determined dimensions, which is inconvenient, as it is then necessary always to be supplied from the same manufacturer of overvoltage arresters.
Finally, this same known device presents another drawback of not lending itself to automatic, robotized manufacture.
It is an object of the invention to overcome the drawbacks set forth hereinabove.